Automatic switching system



O. C. LEVY ET AL AUTOMATIC' swITcHING SYSTEM Aug.. 4, 1936.

Filed Jan. 16, 1952 Inuen :l1-s Dinar- C. La Elm-'anca E. L

Patented Aug. 4, 1936A UNITED STATES AUTOMATIC swrTcInNG SYSTEM Oscar C. Levy, Chicago, and Clarence E. Lomax,

Oak Park, lll., assignors, by mesne assignments,

to Associated Electric Laboratories,

Inc., Chicago, Ill., a corporation of Delaware Application January 16, 1932, Serial No. 587,066v

10 Claims.

The present invention relates in general to automatic switching systems; however. as illustrated, it relates more particularly to the tuning of a radio receiving set from a remotelylocated control station.

A particular feature of the invention lies in the arrangement for supplying current for operating the relays and the ,switch necessary for the remote tuning of the radio-set. This particular feature is not limited to the system shown, but is equally applicable to other automatic switching systems, such as telephone systems, especially small, unattended telephone exchanges. According to this feature of the invention, no operating battery is required, but a rectifier is provided for rectifying the alternating current from a commercial power supply to furnish direct current for operating 'the autom'atic switching apparatus. Arrangements are 'provided so that the rectifier is cut oil' whenever the automatic switching apparatus is not'in use, and is started only when one of the subscribers or operators at a remote control station operates a key to prepare the automatic switching apparatus for use. l .According to another feature of 'the invention as illustrated, a tuning switch may be operated responsive to a digit Adialled at a control station to tune the radio receiving set to a desired station, and, in case the listener wishes to tune theD set to a different station, he dials the digit 0, which returns the switch to normal, from which position it may be again operated responsive to a succeeding digit'to tune in the next desired station. A still further feature of the invention lies in the arrangement by means of which the tuning switch is returned to normal whenever the key at the remote-control station is restored to normal. The power supply to the rectifier is also cut oif when the switch is restored to normal responsive to the opening of the key at the remotecontrol station;

The above and other features of the invention not specifically mentioned at this time will bel come apparent from the the following description and explanation when read in connection with the accompanying drawing comprising one iigure only.

The drawing shows only sufilcient apparatus to enable the presentl invention to be understood. The radio receiving set and associated yof the drawing, and comprises a dial I1, a key K,

and a supervisory lamp I9. This equipment is located at the point from which the radio receiving set is to be controlled. Conductors I and 2 extend to the commercial alternating-currenty 5. supply'source. The relay 5, which is connected in the circuit of the secondary winding of the step-down transformer T, is a relay which responds to alternating current. The automatic switching apparatus shown in the lower portion 10,

of the drawing comprises a plurality of relays and a` tuning switch S. The tuning switch S may be of the rotary line switch type well known in the art of automatic telephony. It comprises an operating magnet 36 and six wipers and as- 15.4 sociated bank contacts. The leads connected tol the bank contacts engaged by wipers 4I to 44, inclusive, extend to the tuning condensers associ'atedw'ith the radio receiving set, and which are adjusted to tune the set to a desired broadcasting station depending upon the position of the wipers 4I to M, inclusive. The four wipers lI-M provide for four tuning stages, one -wiper being individual to each stage. Since each wiper has nine active positions, there are at each stage nine condensers. Considering the iirst tuning stage, for instance, the stage associated with wiper 4I, the nine conductors shown outgoing from the bank of this wiper are connected to terminals of nine condensers, respectively, of 3o the rst stage. The other terminals of these condensers are all multipled together andare connected to the grid of the tube. Since the lament of the tube is grounded when wiper 4| is set on some contact in its bank,'the condenser 35` associated with that contact will be bridged across the grid circuit. The arrangement at each of the other tuning stages is the same.- The .terminals of the windings oi' the various relays and the operating magnet, ,which are des- 40 ignated by a Ininus sign, are connected to a negative bus bar which is connected to conductor I2 extending from the negative terminal of the output circuit of the rectier II. The positive terminal of this rectifier is connected to a grounded bus bar. The off-normal contacts 38, associated with the tuning switch S, are opened when the switch is in its normal position, that is, when the wipers are vengaging the eleventh bank contacts. y Having given a. brief description of the apparatus shown in the drawing, a detailed description of the operation of the same will now be given. It will be assumed that the apparatus is in the condition shown with the tuning switch S at norrent relay 5, back contact of armature I5 andv said armature, conductor 2 I, key contacts I8, contactslof dial I1, conductor 20, armature I6 and its resting contact, to the secondary winding of 'l the transformer. Since the primary winding 3 of transformer T is `permanently connected over conductors I and 2 to the alternating-current supply source, the closing of contacts `I8 of key K completes the circuit for alternating current through the winding of relay 5, which operates, and at armature 6 and its working contact connects the alternating current supply source to the input terminals of the rectifier II.

As soon as the rectifier has built up its voltage to its normal value, the power relay 33 operates from ground at the resting contact of armature 9 and said armature, winding of relay 33 tothe negative bus-bar. At armature 35 and its working contact, relay 33 completes an Obvious circuit for relay I3, and at armature 34 and its working contacts it shunts the contacts of relay 5. The supervisory lamp I9 is also lighted as soon as the rectifier has built up its voltage to normal value. This indicates to the subscriber that the equipment is ready for operation.

Relay I3 operates when its circuit is closed at armature 35, and at armatures I5 and I6 it disconnects the controlconductors 20 and 2| extending to the control station from the secondary winding 4 of transformer T, and connects them in a-circuit including the winding of line relay 22. Relay 5 releases, but the input circuit to the rectifier II is now held closed at armature 34 and its working contact. 'Ihe circuit for relay 22 extends from ground at the working contact of armature I6 and said armature, conductor 20, contacts of dial I1, contacts I8 of key K, conductor 2l, armature I5 and its working contact, winding of relay 22 to the negative bus-bar. Relay 22 operates and at armature 23 and its working contact completes an obvious circuit for the slow release relay 24. Relay 22 operates shortly after the operation of relay I3 and opens the circuit of the sloW-to-operate relay 1, which is completed at armature I4 and its working contact, before this relay has had time to operate. Relay 24 in operating, at armature 26 and its working contact, prepares a circuit for the slow-to-release relay 3|, at armature 25 and its resting contact it opens a further point in the circuit of relay 1, and at the working contact of this armature it prepares the dialling circuit through the operating magnet 36 of the tuning switch S.

When the subscriber at the remote control sta'- tion notes the lighted, condition of lamp I9, he proceeds to dial the digit corresponding to the station to which he desires to listen. It will be assumed that the digit dialled is 5. Accordingly, the contacts of dial I1 are momentarily opened Itive times, and line relay 22 momentarily releases fiive times responsive to the impulses. Each time it releases it completes a circuit from ground, armature 23 and its resting contact, armature 25 and its working contact, winding of relay 21 to the negative bus-bar, and in multiple therewith over the resting contact of armature 32 and said armature, winding of the operating magnet 36, to the negative bus-bar. Relay 21 operates at. the first impulse, and at armature 28 and its resting contact opens the circuit to the lamp I9, and at armature 29 it disconnects groundcfrom bank contact 46 and connects this ground to the wiper 40 of the switch. The function of this-armature will be explained later. At armature 30 and its resting contact it disconnects ground from wipers 4I to i 44, inclusive, thereby disconnecting the tuning condensers so that the radio receiving set will not be tuned to the various 'stations as the tuning switch rotates, thereby causing loud blasts of noise inthe loud speaker.

Operating magnet 36 responds to the five impulses transmitted thereto and steps the wipers 39 to 44, inclusive, of the tuning switch to the rlfth bank contacts. A short interval after the cessa-- tion of 'the impulses, relay 21 releases, and at armature 28 and its resting contact again completes the circuit to the supervisory lamp I9, thereby informing the subscriberthat the tuning operation has been completed. At armature 30 and its resting contact, it connects ground to wipers 4I to 44, inclusive, which in turn extend the ground to the four selected tuning condensers which are adjusted to tune the radio receiving 25 set to the desired broadcasting station. The tuning operation has now been completed and relays I3, 33, 22, and 24 areoperated. As soon as the tuning switch was stepped from its eleventh bank contacts, off-normal springs 38 closed, thereby completing a locking circuit for the power relay 33 to insure the continued operation of the rectilier I I as long as the tuning switch is off-normal.

It will now be assumed that the operator at the remote-control station wishes to tune the radioreceiving set to a different broadcasting station. ToI do this, he first dials the digit 0, followed by the digit designating the desired station. Responsive to the dialing of the digit 0, line relay 22 is released ten times, thereby transmitting ten impulses over the previously-traced impulsingl circuit to the slow-to-release relay 21 and to the operating magnet 36 of the tuning switch Sv. Relay 21 again operates, and at armature 28 extinguishes the supervisory lamp I9. At armature 39 and its resting contact, it disconnects ground from wipers 4I to 44, inclusive, to open the circuit of the tuning condensers, and at armature 29 and its working contact it connects ground to wiper 4I). The operating magnet 36 responds to the impulses, and, in the assumed case with the wipers of the switch standing on the fifth bank contacts, after five operations of the magnet 36, the wipers will be operated into engagement with the tenth set of bank contacts. AWhen the magnet 36 releases to step the wipers into engagement with these bank contacts, a circuit is ,completed from ground at armature 29 and its working contact, Wiper 40, tenth bank contact 48, armature 26 and its working contact, Winding of slow-to-release relay 3|, to the negative bus-bar. Relay 3I operates, and at armature 32 and its resting contact opens the impulsing circuit to the operating magnet 3,6, thereby stopping the switch with the wipers on the tenth bank contacts. Theremaining impulses of the series keep the sIow-to-release relay 21 operated,`but have no effect lupon the operating magnet 36. A short interval after the cessation of the impulses, relay 21 releases, and at Aarmature 28 and its resting contact completes the circuit to the supervisory lamp I9, thereby informing the operator at the control station that he may now dial the next digit. At armature 29 and its working contact, relay 21 opens the circuit Y of the slow-to-release relay 3|, and at the resting 75 the wipers of the switch onto the eleventh bank Aso contacts.

A short time after its circuit is opened at armature 29, relay 3| releases and at armature 32 and its resting contact it completes the impulsing circuit to the operating magnet 36.`

When the subscriber .or operator at the control station notes that the supervisory lamp I9 is again lighted, he proceeds to dial the digit corresponding to the desired broadcasting station. Assuming in this case that the digit is 8, relay 22 momentarily releases eight times, thereby transmitting eight impulses to the slow-to-release relay 21 and to the operating magnet 36. Release relay 21 operates at the rst impulse and performs the functions previously described. Operating magnet 36 responds to the impulses and steps the wipers 39 to 44, inclusive, of the tuning switch S onto the eighth set of bank contacts. A short interval after the termination of the impulse series, relay 21 releases, and at armature 38 and its resting contact connects ground over wipers 4I to 44, inclusive, to the tuning condensers, thereby tuning the radio receiving set to the desired broadcasting station. At armature 28 and its resting contact relay 21 again completes the circuit for the supervisory lamp I9 to inform the operator that the tuning operation has been completed. The radio receiving set has now been tuned to the desired broadcasting station and relays I3, 33, 22, and 24 are operated as in the previous case.

When the operator or subscriber at the remotecontrol station wishes to release the automatic switching apparatus and does not desire to tune in a different broadcasting station, he merely restores the key K to normal, thereby opening the key contacts I8. Relay 22 accordingly releases, and at armature 23 and its working contact opens the circuit of slow-release relay 24, and at the resting contact of this armature prepares a circuit for the slow-toeoperate relay 1. Beforel relay 24 releases, a circuit is completed from ground at armature 23 and its resting contact, armature 25 and its working contact, through the winding of relay 21 to the negative bus-bar, and in parallel therewith over the resting contact of armature 32 and 'said armature, winding of the operating magnet 36 to the negative bus-bar. Relay 21 operates without effect at this time except to extinguish the supervisory lamp I9. The operating magnet 36 energizes in this circuit and remains energized until the 'slow-to-release relay 24 releases. When relay 24 releases,\it opens the circuit to the slow-to-release relay 21 and to the operating magnet 36. The magnet 36, upon deenergizing, advances the switch wipers one step, but this is immaterial at this time.

Relay 24, in releasing, at armature 25 and its resting contact completes the circuit for the slow-to-cperate relay 1 from ground at armature 23 and its resting contact, armature 25 and its resting contact, armature I4 and its working contact, winding of relay 1, to the negative busbar. Relay 1 operates after an interval, and at armature 8 and its working contact locks itself energized independently of armature I4. At armature 9 and its resting contact, it disconnects ground from the terxriinal of the winding oi' relay 33, but this terminal is connected to ground through the off-normal springs 38. At the working contact of this armature, it connects the' ground through the olf-normal springs 38 to the 5 multipled bank contacts I to 9 engaged byvwiper 39 of the tuning switch S. At armature I Il and its working contact it connects ground to the tenth bank contact 46, engaged by wiper 39. The ground connected to the multipled bank contacts I to 9 engaged by wiper 39 is extended over the interruptor contacts 31, through the winding of. the operating magnet 36, to the negative bus-bar. The magnet, therefore, energizes and interrupts its own circuit so that it deenergizes and advances the switch wipers onestep. This intermittent operation of the operating magnet continues until the switch wipers 39 to 44, inclusive. have reached their normal position, whichis the eleventh set of bank contacts. The ground over 20 the interrupter contacts 31 also extends over armature 32 and its resting contact through the winding of relay 21 to the negative bus-bar. I'he relay 21 is, therefore, maintained energized during the return operation of the switch, and at 25' armature 38 and its resting contact it disconnects ground from the tuning condensers to prevent loud blasts in the loud speaker while the switch is returning to normal.

when the switch reaches its normal position, oil-normal springs 38 are opened, thereby disconnecting ground from the winding of relay 33 Y Relay 33 releases, and at armature 34 and its working contact opens the alternating-current supply to the rectier II. itsworking contact, it opens the circuit of relay I3. Relay I3 releases, and at armature I4 and its working contact opens one point in the cire' cuit of relay 1, and at armatures I6 and I8 it again prepares the initial energizing circuit for the alternating-current relay 5.

When` the alternating-current supply is disconnected from the rectifier II, the output voltage drops to zero, thereby removing the 'potential from the winding of relay 1. Relay 1 accordingly releases and at armature 8 and its working co'ntact opens its own locking circuit. At armature 9 and its resting contact it again prepares the initial energizing circuit for thepower relay 33,v and at armature I0 and its working contact it disconnects ground from the tenth bank contact 46. engaged by wiper 39. All oi' the apparatus used in the remote control of the radio receiving set has now been restored to normal, and the alternating-current supply has been disconnected from the rectifier. Thus it is seen that when the apparatus is not in use, the rectiiler is cut olf so that normally the apparatus does not consume any current. Furthermore, no battery is required, thereby eliminating the attengili necessary to keep the battery charged at all What is claimed is:

1. In combination, a step-by-step selecting switch, operating means for said switch, a recti- 55 iler for supplying operating current to said switch, an input circuit for said rectier includ- .ing an alternatingecurrent supply source; a remotely located control station, a line extending from said station and normally connected to 4calci 70 alternating current supply source, anvalternating current relay connected in series with said line in circuit with said source andoperated in response to the closure of said line at said station, contacts on said relay for closing said. input cir- It At armature 36 and 35.'

cuit, a direct current relay connected to said rectifier and operated when-the output voltage of said rectifier attains its normal value, contacts on said direct current relay for shunting said first-mentioned contacts, means controlled by said direct current relay for transferring said line to said switch operating means, said switch operating means thereafter operated by intermittently opening said line to operate said switch to make a. selection, and means for holding said direct current relay energized until the circuit over said line is opened for a prolonged period of time.

2. In an automatic switching system, a line, a step-by-step switch having a normal position and selecting positions, a normally inactive current source for supplying operating current to said switch, means responsive to the closure of said line for starting said current source, means forv continuing the source `in operation after it is started, means controlled over said line for thereafter operating' said switch step by step from normal position to dierent selecting positions, means for restoring said switch to normal position in response to opening said line, and means for automatically cutting off said current source when said switch is restored to normal responsive to the opening of said line.

3. In an automatic switching system, a line, a step-by-step switch having a normal position and selecting positions, a rectiiler for supplying operating current to said switch, a normally open input circuit for said rectifier, means'responsive to the closure of said line for closing said input circuit and for connecting said line to the operating means of said switch, said switch operating means for operating said switch from the normal to one of said selecting positions by impulses transmitted over said line, restoring-means for said switch,means operated responsive to a prolonged opening of said line for operating the restoring means of said switch to restore said switch to normal, and means operated responsive to said switch reaching its normal position for opening said input circuit.

4. In an automatic switching system, a line, a step-by-step switch having a normal position and selecting positions, normally inactive means for supplying operating current to the operating means of said switch, means responsive to the closure of said line for rendering said supply means active, means when the output voltage of said supply means has attained its normal value for connecting said line to said switch operating means, said switch operating means thereafter controlled over said line foreperating said switch from normal to one of its selecting positions, restoring means for said switch, and means eilective when said line is opened for more than a predetermined length of time for operating the restoring means of said switch to restore said switch'to normal, for again rendering said supply means inactive, and for .disconnecting said line from said switch.

5. In an automatic switching system, a station equipped with a dial, a line extending from said station and terminating in automatic switching apparatus including a rotary stepping switch having a normal position and selecting positions, normally inactive means for supplying operating current to said switch and apparatus, means re'- sponsive to the closure of said line for starting said current supply means, means for operating said switch from normal position to a selecting position responsive to a dialled digit, means for restoring saidswitch from its operated position to its normal position responsive to the dialling of a particular digit irrespective of the position to which the switch was previously operated, means responsive to the prolonged opening of the 5 line for operating the restoring means of said switch to restore said switch to its normal position, and means responsive tothe restoration of said switch for rendering said current supply means inactive. l 6. In an automatic switching system, a station equipped with a dial, a line extending from said station and terminating in automatic switching apparatus including a stepping switch having a normal position and selecting positions, a rectifier l `for supplying operating current to said switch and apparatus, means responsive to the closure of said line for starting said rectifier, means for operating said switch from its normal position to a selecting position responsive to a dialled digit, means for restoring said switch from its operated position to its normal position responsive to the prolonged opening of the line and responsive to the dialling of a particular digit, and means responsive to the restoration of said switch to its normal position only in case it was restored responsive to the prolonged opening of said line for cutting ofi said rectifier.

` '7. In aswitching system, a step-by-step switch having a normal position and selecting positions, a normally inactivesource of direct current for furnishing operating current to said switch, a line, means responsive to 'the seizure of said line for rendering said source active, a relay normally bridged across said source andoperated when said source is rendered active, means' controlled by said relay for maintaining said source active independently of said line, means controlled over said line for operating said switch from its normal position to a selecting position, in response to the operation of said last means a second relay,

means responsive to the opening of said line for operating said second relay, means for restoring said switch from its operated position to normal in response to the operation of said last means, and means responsive to the operation of said second relay and the restoration of said switch for releasing said first relay to render said source inactive, said second relay upon operation bridging itself across said source and releasing as soon assaid source becomes inactive.

8. In a switching system, a stepping switch having a normal position and selecting positions, a normally inactive rectifier for supplying operating current to the bus-bars to which said switch is connected, a line, an alternating current relay connected to said line and operated in response to the closure of said line to start said rectifier, a second relay normally bridged across the busbars and operated as soon as said rectifier builds y up its output voltage to normal value to maintain said rectifier Ain operation, means-operated responsive to the operation of said relay for transferring said line from said alternating current relay to said switch so that said switch may be operated over said line to a selecting position, a third relay, means responsive to the opening of said line for bridging said third relay across the bus-bars and for restoring said switch from its operated position to normal, and means responsive to the operation of said third relay and the restoration of said switch for releasing said second relay to cut on said rectifier, said third relay releasing when l(the output of said rectifier has fallen to zero to again bridge said second relay across the bus-bars.

9. In combination, a control and a remote station, a line connecting the two, a transformer in the remote station, a sourcevof power connected to the primary of said transformer, a rectifier in the remote station, means at the control station for completing a circuit including the line the secondary of the transformer, and means in the remote station responsive to the closure of said circuit for connecting said source to the input side of the rectier, means operated over the output side of said rectier in response to the rectirer building up a predetermined voltage for releasing said last means and for substituting means for maintaining said source connected to the input side of said rectifier independent of short openings in said line by impulses transmitted thereover, a step-by-step selecting switch having a plurality of selecting positions, and means thereafter jointly controlled by impulses transmitted over said line and by the output of said rectifier for directively operating said switch to one oi its selecting positions, said maintaining means rendered inoperative by a longer opening of the line.

10. In an electrical control system, a step-bystep selecting switch having a plurality of selecting positions, a normally inactive source of direct current for supplying operating current to said switch, a line, means responsive to the closure oi' said line for rendering said source active, a relay normally bridged across said source and operated 10 to one of its selecting positions, means controlled 15 by said relay for maintaining said source active independently of said short opening of saidiine, and means thereafter controlled over said line for releasing said switch from its operated position and for releasing said relay to render said 20 source inactive.

OSCAR C. LEVY. CLARENCE E. LOMAX. 

